FNQFLYER

Overspeeding with a Saito? Hsukaria I assume you are not pushing the limits of performance and a simple cure to that comes in 3 parts, richen the mixture, use the travel adjustment facility on your T/x and mess around with props. I note you are doing the later but I would try different prop diameters as well as pitch. I assume you are using a "standard" fuel mix. I personally have never "oversped a Saito" just got more revs out of them

hsukaria

Sorry, I meant overspeeding the plane, not the engine. It is a 3D plane that is prone to flutter if run too fast.

Hobbsy

My Feedback: (102)

I'd be real curious as to whether the 1.15 was actually more powerful than the 1.00, the 1.15's benchmark prop is listed as 15x6 @ 8,800. The 1.00's bench mark prop @ 14x8, no rpm listed. I'd think the 1.00 would turn the 15x6 at 9,000 or better. The 1.00 also has a longer stroke although that doesn't always count for much.

hsukaria

I was pursuing the 100 instead of the 115 because I didn't know it is heavier than the 115. I am constrained by engine weight in the Extra, I have the battery as far back as possible and 1 oz of weight in the tail using the 91S. So, the engine I will pursue is the 115, someday, if a good deal comes my way.

My Extra with the 91S weighs 7 lbs 11 oz. My U Can Do 46 weighs 5 lb 12 oz. I fly the U-Can-Do at 1/4 max unless hovering or going vertical. So, I'll try the 14x4W just for kicks.
A 115 on a 8.5 lb Cub would be insanely overpowered, so it should be fun. I bet an FA-82 would be more than enough.

72

Need some help with a Saito 100. I bought this engine used online and it looks to be in very good shape with good compression. I have decided to replace the bearings as there is some endplay in the crank and I like new bearings to start with anyway. There is no carbon buildup in the cylinder and the valves look perfect. I flew several flights with the engine yesterday and then disassembled it tonight. When I removed the exhaust valve cover, it and the pushrod from the camshaft were completely full of what looks like exhaust oil. Never seen that before. Any ideas? Is this bad or not?

Hobbsy

My Feedback: (102)

72, it sounds like the 1.00 was run inverted for much of its life, my guess it just needs good clean up. The new bearings are $11.88 and fre shipping at BocaBearings. I just put new ones in my 1.00 about 2 months ago.

HS, I wasn't trying to discourage you on the 1.15, I was mostly thinking out loud. I installed a Hall Effect sensor and trigger magnet on my 1.00 today. Results may be forth coming tomorrow. I'll have to steal the CDI from the 1.50 until I can afford a system for the 1.00. The other C&H Ignition I have does not have SynchroSpark. Dan has set me off on a new kick.

72

Hobbsy, thanks for the quick reply. I will have it back together tomorrow and run it. See what happens. Let you know if this clears the problem.

Hobbsy

My Feedback: (102)

72, if you don't mind give us the whole skinny, prop, fuel, plug, max rpm, idle rpm etc, it's all good stuff to read. Thanks

Hobbsy

My Feedback: (102)

http://sceptreflight.net/Model%20Eng...%20FA-100.html

Here is Clarence Lee's test of the 1.00if you're curious.

blw

My Feedback: (3)

I think the 91 fits between the 82 and 100 for prop sizes. You have a good choice with those three engines.

72

72, if you don't mind give us the whole skinny, prop, fuel, plug, max rpm, idle rpm etc, it's all good stuff to read. Thanks

Will do.....

SrTelemaster150

When you take 2 engines of equal displacement that have different bore dimensions, the engine with the larger bore will usually make more HP. In this case the FA-115 not only has a larger bore, but also a more displacement. That would mean that is would most likely make substantially more power.

Generally speaking, increase displacement by an increase in bore usually make for more HP increase than a similar increase in displacement via stroke, especially at the RPM ranges we are operating in.

Increaseing the bore increases volumetric efficiency, hence better breathing.

Since we aren't required to pull weight through a direct mechanical coupling like an automobile or truck, the longer stroke wouldn't account for that much if an advantage. We're not pulling stumps here.

I set up & tested an FA-125 recently. I was not impressed with the performance over my FA-91S. While the FA-100 shares the same stroke as the 125, the FA-115 has the same bore as the 125. I would suspect that the FA-115 would be far closer to the 125 in power output than compared to the 100.

Rudolph Hart

Hi huk as trev (fnq) said you can always throttle back and keep the 14x6 on the u can do.Re cg almost all my saito engines are fitted with the carby hard up against the firewall.You should buy a 115,it will easily equal for fox 74 in the real world.

72 welcome looks like you've made a good start with the 1.00 and you are happy with it.If there was no carbon build up in the cylinder and the valves looked perfect the previous owner must have been running some castor and it's quite normal to have lots of oil around the exhaust valve even when the engine is sidemounted.

Sr huk has a good point,your j3 will be insanely overpowered with a 115 but that's the way i like it.Hope you have the clipped wing version.

Dave i wish saito would say what prop they use for all of/instead of some of their benchmark figures.As you know i have a 115 in a stumpy nearly 10# (some unkindly say brick) cmpro midget mustang.The midget absolutely hammers along and noticeable prop torque with a mas classic 15x8 which pulls middle eights on the ground with shop bought fuel,no special mixes.It rips prop tips in flight and the first time i heard that i thought it was the biggest backfire i'd ever heard and that i'd lost a prop.But the 115 in this aeroplane flies best with a mas q tip 14x10

Hobbsy

My Feedback: (102)

Dan and Pete, I think the 15x6 rating for the 1.15 @ 8,800 has to be a misprint. In the Clarence Lee test of the 1.00 I linked above, the 1.00 turned a 15x6 at 9,700 as i had suspected. The 1.15 probably should read 15x8 @ 8,800..

We tend to forget that the term longer stroke doesn't automatically mean more torque, it usually means it's just in a different place in the rpm band.

acdii

Speaking of 100, got mine running again on the Stang, and running sweet as day one. Haven't flown it yet, when it pitches over on its nose with just a little power and full up elevator, thats a sign not to fly it just yet. Have to rip the tail apart and replace the feathers.

Hobbsy

My Feedback: (102)

Here is a shot of my 1.15 before I ran it. There was molybdenum grease in the crankcase. I looked in there because the black grease had scared another poster., he didn't know what it was. It took about 10 minutes running to wash it all out.

I found two post concerning 1.15 rpm, one showed a 1.15 with a 16x6 @ 9,000 rpm and the other a 1.15 with a 15x8 APC @ 8,700.

AC, glad it's purring.

AeroFinn

Dear friends

Just an update: I'v now run 4 gallons through my FA-125 and now it seems to have loosened up.:

The fuel: 15% nitro + 17% Aerosave full synthetic

The engine purrs like a cat at 2300-2400 for 5 minutes or more after a flight. It does idle lower but sems to quit eventually after 1-2 minutes if I go to about 2100 rpm. This is with an apc 15x6 prop.

The needles are perfect now. If I try to lean the low end by 5 minutes the engine dies on quick acceleration.

P.S. I flew the thing on Saturday and the figures are from that day. I then flew the model again yesterday and the engine idled 200 rpm lower on the same throttle trim setting. I notced this each time I landed the model and checked the rpm.

This must be due to the glow ignition which is effected by the different air pressure, temperature etc.

I wonder if the idle rpm will be more consistent from day to day once I'v switched to CDI?

hsukaria

Just based on my limited experience, I run my FA-91S with either a 15x6 or 14x8 and it idles well consistently. What I limited it to is around 2500 rpm, anything lower would mean that I have to lean the low speed needle more. That would translate to either the engine quitting when throttling up (you mentioned that too), or having to adjust the high speed needle richer. I caught that a couple of times on my enignes, I tune the low speed needle too lean, then I have to compensate with the HSN a bit rich. The engine seems too rich at WOT when that happens.

Another thing, it may be that your prop may be on the smaller side. The prop acts as a flywheel and helps to steady the idle speed. I would try a bigger prop and set the idle at around 2500 rpm, not lower.

blw

My Feedback: (3)

Aerofinn- it sounds like my 125. That sounds like Saitos. I always tach my idle speed when I land, not when just cranking up. There's a correlation pointed out here if you remember the Saito remark about setting the valve lash when cold. Temp and density altitude means everything to engines, internal combustion and turbines, so you are dealing with that too. Since you have so much fuel burned through the engine I'm betting that if you have a prop within the ballpark of being right, and if you could tweak your low speed 1/32 of a turn leaner you could get a reliable 2100 rpm idle. This is assuming you have clean nipples (don't say it Old Fart!) good inside diameter on all of your fuel lines, good tank height, etc. There's no denying that an APC would help matters.

blw

My Feedback: (3)

Dave, I was never impressed with Clarence Lee's prop selections but I understand why he did it that way. And, he started out a long, long time ago and kept things consistent. He began mentioning APCs in later reviews and recommended those outside of his test parameter props.

You are right about the power being in a different spot, but that is a significant thing. That extra power of the 1.15 in the Cub is very useful. All it takes is a small, slow blip to pull out of an incipient stall or to get the plane to turn at the top of a stall turn whereas a 2 stroke takes more drastic measures. The low end torque is invaluable for stuff like that.

But, you can move that power band some with prop diameter selection. Not pitch, but diameter. Okay, maybe some with pitch change, but diameter is the big factor.

SrTelemaster150

FA-91S CDI, 15% Cool Power Glow Fuel, 15 X 5 Zinger Propeller

Ignition Advance Setting = 35° BTDC
Minimum Reliable Idle = 1700 RPM
Maximum RPM @ WOT= 9700 RPM
Fuel Consumption @ WOT = .65 oz per minute.

AeroFinn

Hsukari and blw

Thanks for your comments. 1/32 of a turn equals about 5 minutes? right? No way I can lean the engine that much it will die on acceleration. But to be honest I do not have any issues with 2300-2400 rpm idle as my pitch is 6" so I can slow down on landing nicely. I also think the Aerosave being extremely good with it's lubinq qualities the side effect is it takes a forever to get the engine run in. I mean, really run in.

And like I said I'm looking forward to having time to experiment with my N.IB. CH -Ignitions CDI kit

My objective is to have a more consistent low idle (I just adore the nice low idle sound of Saitos) from day to day. I can now realize no matter how I tune the engine even modest changes in athmospheric conditions seem to effect on idle. I hope this modest variation of the engine idle charactersistics from to day to day will disappear along with the CDI. I don't really care about fuel consumption or top rpm although performance improvemet never hurts..

So to sum up I think those people how say "I never or very seldom need to touch the needles of my engine" are those fellow modellers who are happy with good performing engines but do not expect their engines to run perfect every time on the field.

But then again, this is just me & my thoughts..

Cougar429

My Feedback: (3)

SrTelemaster150, I agree with a lot of what you stated regarding bore size/HP, but there are many other factors that will affect your power output beyond just that measurement.

Volumetric efficiency is a calculative value and does not always play by the numbers. Even if you ignore environment, in the end valve size, orientation, overlap and timing/RPM will have a major roll in how the engine breathes. Same with intake and exhaust size and length and if they are tuned to work best at the specific RPM you need.

Back in my auto days, I pulled a 429 from a police cruiser and stuffed it in my Cougar, (hence my handle). Engine specced at 400 HP out of the crate, but due to intake bore size and cam it did not get into the power band until above 3000 RPM. Not really useful for every day commuting. By dropping in an RV cam things were much more docile. Back then, the "Holy Grail" was to hunt down a set of 428 con rods to get the L/R, (length of rod vs stroke) ratio to 1:1.

We also used another little trick. By yanking out the cam from pretty much any carburated GM 305-350 smog motor and dropping in one from a 67 L79 327 the output measured on a dyno increased considerably.

There have been MANY ideas tried over the years, with the most current Chrysler "Corporate" V6 having variable valve timing to optimize output over the wider power band requirements. This puts out over 30 HP more than my 2010 4.0, but I have more TORQUE.

In regards to how this affects our Saitos, I may be suffering with the "Caffeine Low" light on, but would suspect a larger bore would spin the same prop faster or be able to turn a larger diameter prop the same RPM, but think a longer stroke would be able to carry that RPM better as load increases, (vertical).

Hobbsy

My Feedback: (102)

I just ran about 14 OZ of fuel through the CDI equipped 1.50.

Engine, Early 1991 or 92 Saito 1.50 with 11.24 to 1 compression ratio.
Prop== Master Airscrew Classic 18x6\
Fuel==WildCat 15% with 18% syn/castor blend
RPM peaked===8,150
Idle 1,600, not optimized yet, linkage issue
CDI set at 35 btdc
Even with ignition it can still kick the prop off if leaned too far.

That prop sure makes a big wheel. As the Beav would say, this pitcher wuz tookin at 5,000 rpm's
Again it was as smooth as silk, clean midrange and quick acceleration.

hsukaria

Even if you have 2 engines with the same max power, their torque peaks might be at different RPM ranges. I think a long stroke design will help achieve the torque peak at lower rpms, which is useful in trucks or 3D airplanes for vertical/hovering. Racing engines have short stroke and big bore engines to achieve power at higher rpms. Like you said, there are so many variables, including transmission gear ratios or propellers sizes for planes. It is all these variables that affect total performance.

Adding CDI may help reduce ambient environmental effects on engine behavior, but with the cost of added weight and complexity. It's fun to tinker with these engines, and a lot easier and cheaper to do it on a 1 c.i. engine instead of a 429 c.i. engine, right Cougar429?